1. Field of the Invention
This invention relates generally to insulated-gate type semiconductor devices, and more particularly, to an insulated-gate type semiconductor device having a built-in protection circuit.
2. Background Art
Insulated gate bipolar transistors (hereinafter referred to as IGBTs) have been widely used as fast switching elements. IGBTs have been developed as desirable switching elements which have both advantages of a low on-resistance characteristic of bipolar transistors in their ON state and a fast switching capability of insulated gate field effect transistors (hereinafter referred to as MOSFETs).
When any fault occurs in the main circuit of an IGBT during its operation, its elements may break down due to an excessive current or voltage. In such an instance, it becomes necessary to provide for a protection circuit which will start its operation to protect the IGBT before it breaks down. In such a protection circuit, an overcurrent or overvoltage detection element (which will be referred to as detection element) coupled to the IGBT is adapted to detect occurrence of any abnormality, then, the gate voltage of the IGBT is controlled accordingly to protect it from breakdown. This protection circuit of the IGBT is comprised in conjunction with an IGBT, diodes and transistors, resistance, capacitors and the like, and is provided mostly in a module or package.
On the other hand, there is a great demand for reducing the size of power conversion equipment utilizing IGBTs, thus, many attempts have been made, and continue to be made to integrate such protection circuit configurations or mount it on one chip. With respect to the above-mentioned protection circuit, it has been desired to integrate it into the IGBT's internal configuration so as to be provided in a single chip, and such an example has been already disclosed in the Japanese Patent Application Laid-Open No. 4-361571. This detection element built-in IGBT is provided with a carrier drawing or extracting portion which is disposed between a main IGBT region and a detection IGBT region for preventing a current concentration into the detection IGBT, within an area surrounded by this carrier extracting portion (hereinafter referred to as a partitioning portion) the detection IGBT is formed so as to improve linearities of a detection current and the main current.
According to the foregoing detection element built-in IGBT, however, since only the detection IGBT is formed within the partitioning portion, a separate protection circuit is required, further requiring wiring from the detection IGBT to the separate protection circuit outside the partitioned area. Accordingly, due to wiring resistance and wiring inductance thus added, there occurs a time lag from detection of an overcurrent to the operation of the protection circuit, causing a problem that precision and reliability of the protection operation area is lowered. There is another problem that the provision of the partitioning portion results in an increase in the size of a chip.